The preparation of polyhydroxy fatty acid amide surfactants by the reaction of fatty esters with N-alkylamino polyols is of considerable commercial interest. However, the resulting N-alkylamido polyol reaction products, such as the fatty acid N-methyl glucamides, are often contaminated with residual amounts of unreacted N-alkylamino polyols. Contamination by such materials may be tolerable under many circumstances. For some uses, however, the presence of unreacted N-alkylamino polyols may be undesirable for color and odor reasons. In particular, the manufacturer of modern, clear, colorless, high sudsing detergent compositions which contain polyhydroxy fatty acid amide surfactants (e.g., C.sub.8 -C.sub.22 fatty acid amide derivatives of N-methyl glucamine or N-methyl fructamine) requires an inexpensive source of such materials which have desirable low amino polyol levels. In addition, the manufacture of such detergent compositions, especially the colorless versions, sometimes employs various bleaching agents, such as H.sub.2 O.sub.2, which could potentially oxidize the residual N-alkylamino polyols to undesirable by-products. Manufacturers presumably could arrange for special care to be taken during the reaction in order to minimize the levels of such unreacted starting materials, or employ separate purification techniques. However, the manufacturer of high volume, low-cost chemicals such as home-use detergents can ill-afford special handling techniques or materials which require expensive purification steps.
The present invention solves the heretofore unappreciated problem of contamination by sources of N-alkylamino polyols associated with the manufacture of polyhydroxy fatty acid amides, and thereby affords access to a high quality supply of this class of surfactants which are especially useful in situations where oxidants may be present.